Circuit interrupters are electrical components that can be used to break (or open) an electrical circuit, interrupting the current flow. A basic example of a circuit interrupter is a switch, which generally consists of two electrical contacts in one of two states; either closed, meaning that the contacts are touching and electricity can flow between them, or open, meaning that the contacts are separated, and no electricity can flow between them.
Another example of a circuit interrupter is a circuit breaker. A circuit breaker may be used, for example, in an electrical panel to limit the electrical current being sent through connected electrical wiring. A circuit breaker is designed to protect electrical wiring and associated electrical components from damage caused by an overcurrent condition such as, a short circuit or a ground fault (collectively referred to as a fault condition). If such a fault condition occurs in the electrical circuit, the breaker will trip. This will cause a breaker that was in the “on” position to flip to the “off” position and interrupt the flow of electrical energy through the circuit breaker. When a circuit breaker is tripped, it may prevent a fire from starting on an overloaded circuit; it can also prevent damage to or the destruction of any devices that are drawing electricity from electrical circuit.
A standard circuit breaker has a terminal connected to a power supply, which may comprise electrical power provided by a power company. A standard circuit breaker also typically includes another terminal to which is connected to the electrical circuit that the circuit breaker is intended to protect. Conventionally, these terminals are referred to as the “line” and “load” terminals respectively. The line is often referred to as the input into the circuit breaker; whereas the load is often referred to as the output. The output supplies electrical energy to the electrical components connected to the electrical circuit.
A circuit breaker may be used to protect an individual device, or a number of devices. For example, an individual protected device, such as a condenser unit, may be directly connected to a circuit breaker. A circuit breaker may also be used to protect multiple devices by connecting to multiple components through wiring that terminates at electrical outlets. In this manner, the circuit breaker feeds electrical power to all the devices connected to the circuit via the outlets (e.g., a lamp, a television, a computer, a plug in air conditioner, etc.). In other configurations, circuit breakers may be for special use, for example, they may be provided in a rack in a server room where a specific number of servers are connected to a particular circuit breaker.
A circuit breaker can be used as a replacement for a fuse. Unlike a fuse however, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Circuit breakers are generally considered safer to use than fuses. For example, in a situation where a fuse blows, interrupting power to a section of a building for example, it may not be apparent which fuse controls the interrupted circuit. In this case, all of the fuses in the electrical panel would need to be inspected to determine which fuse appears burned or spent. This fuse would then need to be removed from the fuse box, and a new fuse would need to be installed.
In this respect, circuit breakers can be much simpler to use than fuses. In a situation where a circuit breaker trips, interrupting power to a section of a building, for example, it may be easily apparent which circuit breaker controls the interrupted circuit by looking at the electrical panel and noting which breaker has switched off to the tripped position. Conventional circuit breakers include a switch on the face of the breaker where the switch is moved toward the center of the electrical panel for “on”, toward the perimeter of the electrical panel for “off” and will reside in a center position for a “fault.” This breaker can then be visually identified and reset. If the circuit breaker is in a fault state, the handle needs to be moved to the “off” state and then to the “on” state and power will be supplied to the connected electrical circuit.
In the circumstance in which a circuit breaker has tripped due to a fault, it is relatively easy to determine which breaker is tripped by a visual inspection. However, there is no information available as to what caused the overcurrent that caused the circuit breaker to trip, or whether or not the circumstance that led to the overcurrent still exists. The only way to determine this is to reset the breaker by turning it off, and then on. If the breaker immediately trips, the fault condition is still present. However, applying voltage to the circuit to test to see if a fault condition is still present is not an optimal solution.
Additionally, in the event of a tripped circuit breaker, a technician will in all likelihood, have to physically inspect the circuit and connected loads. In the event that the circuit feeds multiple outlets, the technician will typically unplug all the connected devices and reset the circuit breaker. If the circuit breaker trips, this tells the technician that a problem is likely with the wiring itself. If the circuit breaker does not trip, then the problem is likely with one of the connected loads. The technician can then iteratively connect and disconnect the loads to determine if one of the loads is causing the fault. Again, applying a high voltage for testing purposes is not ideal. Alternatively, if each of the loads is attached sequentially and the circuit breaker does not trip, then it could be that the total load on the circuit breaker exceeds the current rating of the circuit breaker and the loads would have to be connected elsewhere. However, this is a time consuming process, requires a technician to be on site to perform the testing and uses line voltage for testing purposes.
In the event that the circuit breaker feeds a hard wired connected load, such as a roof top condenser unit, the technician can disconnect the load and work through an iterative process to determine where a fault might exist in the circuit. Again, this approach uses line voltage as a test voltage and depends on the circuit breaker to trip in the event of a fault condition.
Another problem with the above approach is that no information beyond the fact that there is a fault that is causing the circuit breaker to trip, is obtained from the above-described method.
Still another problem is that, using a circuit breaker as a power switch or a diagnostic tool subjects the breaker to a greater number of operational cycles than it would otherwise experience in a typical circuit protection application. This can result in an unacceptably premature failure of the circuit breaker. Typical circuit breaker mechanisms are designed to survive only 20,000-30,000 cycles before failure. In order to increase the number of cycles that such circuit breakers can endure before failure, all of the components of the circuit breaker must be designed in a more robust way than would otherwise be required. This increases the cost of producing the circuit breaker.
Still another problem faced by loads that are connected to circuit breakers is that, circuit breakers are designed to trip once a current rating is exceeded. In other words, the circuit breaker is sized to protect the wiring that feeds electrical current to the load(s) connected to the circuit. This means that a connected load may begin to draw more current than it is designed to because of, for example, a problem with the load, but if the current draw does not exceed the current rating for the circuit breaker, electrical power will continue to be provided to the load (i.e., the circuit breaker is protecting the wiring from overheating, not the load connected to the wiring). As can then happen, eventually the load becomes more and more damaged until finally catastrophic failure of the load occurs, which then does cause an over current condition thereby causing the circuit breaker to trip. However, the damage is done and the connected load is irretrievably damaged.
It is therefore desired to provide an alternative system that is usable with a circuit interrupter that overcomes the aforementioned limitations.